Material and fatigue properties of old metal bridges

Abstract: This thesis aims to answer questions regarding material and fatigue properties of bridges built between the end of the 19th century to 1940's. Regarding material properties the study involves the creation of a data base consisting of material properties of bridges. The establishment of a data base was done by retrieval of test certificates from material investigations conducted on existing bridges. The bridges in question were road and railway bridges produced before 1940's. The aim of the investigation was to determine the material properties of bridges in the specified interval and compare these with properties in evaluation codes. From the evaluation of the data base it became apparent that the yield strength of the existing bridges was higher than specified in the evaluations codes of Sweden and Denmark. Also a big divergence regarding the toughness properties were established for the investigated bridges. Regarding fatigue endurance, a literature survey of fatigue tests performed on riveted structureswere conducted. The survey concerned both full scale structures retrieved from bridges taken out of service and small scale tests. The objective was to investigate the fatigue resistance of riveted structures. Factors as hole preparation, corrosion, clamping force and influence from materials properties on the fatigue performance was also inquired. In the evaluation of the fatigue tests it was concluded that fatigue endurance of riveted assembled girders was best described by the detail category C=63.